Make sure all functions used in libsandbox.c is declared static. Define
SB_STATIC in localdecls.h for this. Include sandbox_futils.c rather than
linking with its object. Hopefully this will fix bug #90153.

Fixup the constructor/destructor function names again (they should be _init()
and _fini() it seems, and not being called caused sandbox_lib_path to be
unset, and thus breaking the execve() wrapper's LD_PRELOAD protection).
Add both the path in given SANDBOX_x variable, as well as its symlink
resolved path in init_env_entries(). Modify filter_path() to be able to
resolve paths without resolving symlinks, as well as to be able to resolve
symlinks. Fix a possible segfault in check_access(). Add symlink resolving
to check_access() resolving bug #31019. Add 'hack' for unlink, as the fix
for bug #31019 cause access violations if we try to remove a symlink that is
not in protected path, but points to a protected path. Fix a memory leak in
sandbox.c (sandbox_pids_file in main()). Fix the realpath() calls in main()
(sandbox.c) being unchecked. Fix the debug logname not having the pid in it
(pid_string was uninitialized). General syntax cleanups.

Fix inverse test logic in canonicalize.c, use a strncpy. Fix gcc warning in
getcwd.c. Add symbols.in and logic to Makefile.am to generate symbol versions
for glibc and other libc's that use this. Update libsandbox.c to use these
symbol versions if available. Fix exec wrapper to re-export LD_PRELOAD if the
process unset it.